Packet Switching vs Circuit Switching
Circuit Switching - In the figure below, there are 3 sources and 3 destinations, which depict mobile phones. The black dots are the nodes or routers that transfer data (including voice) from the sources to the destinations. Let's consider that Source 1 calls Destination 2. Say, the blue path gets established for the call. Similarly, Source 3 calls Destination 3 and the red path gets established. Now if Source 2 wants to make a call, there are no free nodes to handle the call, assuming that each node can serve only one line at a time. Hence Source 2 and Destination 1 are cut out from the network until any one of the other 2 calls terminate. In circuit switching, a dedicated path (or channel or circuit) is set up for a call, between source and destination. This path lasts as long as the call lasts. GSM (Global System for Mobile Telecommunication) uses circuit switching for serving calls. This illustration is a typical circuit switched network.
Packet Switching - On the other hand, if this same network was a packet switched one, then the case would be different. The sources depict mobile phones, while the destinations depict the internet servers, from where information (web pages) is obtained. If Source 1 requests some information from Destination 2, this request is converted into packets of data and sent to the destination. Similarly, Source 3 requests Destination 3 for information, which is sent in the form of packets. The nodes are equipped with additional hardware and software to handle these packets, i.e. to determine where the packets need to be routed. There is no dedicated path set up between source and destination. Therefore, after a node transfers a packet, it is free to handle the next packet. Now if Source 2 wants to access information from any destination, it can do so without being cut out of the network. One thing to note here is that the packets might not take the same route to reach the destination. Their paths are determined on the fly, depending on which nodes are free. Hence they may arrive at the destination in a shuffled order. Therefore an assembler is required at the destination to put them in order.
GPRS and packet switching detailed in What is GPRS?
GSM and circuit switching detailed in What is GSM?
GPRS vs GSM (packet switching vs circuit switching)
| Packet Switching (GPRS) | Circuit Switching (GSM) |
| Dynamic path is determined for the packets on the fly depending on which nodes are free. | Static or dedicated path set between source and destination for the entire duration of the call. |
| Efficient network usage | Network not as efficient as packet switched. |
| The same number of routers can serve multiple sessions. | The same number of resources can serve limited sessions. |
| Lesser chances of user getting cut out of network. | If all lines on the network are busy, user will not be able to use network until resources are freed up. |
| Plenty of overhead for assembling, streaming, buffering etc. Plus additional hardware and software required for enabling dynamic routing. | Overhead is not as much as packet switching. |
| Billing is done on the amount of data transferred over the network. | Billing is done on the amount of time spent on the network. |
